Guest post by Christopher Darnton The United States and Cuba have reached a historic agreement, putting an end to a half-century of frozen relations. Reciprocal speeches by Presidents Barack Obama and Raúl Castro, and gestures like the exchange of high-profile prisoners convicted of espionage, suggest that the two countries will open not only embassies but also a new horizon of potential cooperation between their citizens, and will uproot the last vestiges of the Cold War in the Americas. The historical record of international rivalries and conflict resolution efforts in the Western Hemisphere confirms that this policy shift is truly impressive. However, previous diplomatic breakthroughs also suggest the need to temper expectations regarding both U.S.-Cuban relations and Cuban regime change, particularly in the short run. Rapprochement is a significant achievement, but it is more fragile, and less transformational, than we might think. The litany of overt and clandestine U.S.-Cuban dialogues since the 1959 revolution, and their paltry record of isolated tactical cooperation and unabated rivalry, casts last week’s events into particular relief. This is a major shift, unquestionably. This is consistent with other Latin American cooperative breakthroughs, such as between Argentina and Brazil in 1980, which were frequently preceded by a series of failed overtures. However, Latin American rapprochements also suggest that deepening cooperation is neither immediate nor automatic. Committed diplomacy and ongoing common interests are important to avoid backsliding into acrimony. Regionally, this turning point in U.S.-Cuban relations has been met with both surprise and acclaim. Latin American diplomats had tried unsuccessfully to bridge the Washington-Havana gap for generations. In the year and a half between the Bay of Pigs invasion and the Cuban Missile Crisis, for instance, leaders from Ecuador, Argentina, Brazil, and Venezuela tripped over one another in pursuit of reuniting the hemisphere (and of the prestige accruing to successful mediators). Transcending U.S.-Cuban conflict would make inter-American cooperation easier on several fronts. However, the hemisphere retains ideological, economic, and geopolitical fault lines, including divergence between Mexican, Venezuelan, Brazilian, and North American worldviews and an expanding array of competing trade blocs and security partnerships. Cooperation is not harmony. Globally, although Pope Francis deserves credit for successful mediation between Havana and Washington, countries often turn to third parties because they are unable to resolve their differences directly. The Vatican is well positioned to act as a peace broker in the—largely Catholic—Americas. Under Pope John Paul II and Cardinal Antonio Samorè, for example, the Vatican mediated conflict between Argentina and Chile from 1978 to 1984. However, Vatican involvement suggests serious limitations on any U.S.-Cuban consensus. Also, third parties’ influence is often circumscribed: the Vatican may be effective on prisoner releases and humanitarian issues, but may have less influence over the ongoing trade embargo, which is rooted in American domestic politics. Rapprochement is commonly a presidential affair that can run aground on bureaucratic, legislative, or societal opposition. Although the U.S. State Department will occupy an embassy in Havana for the first time since the 1960s and implement much of the new U.S.-Cuban political relationship, President Obama seems to have relied on advisors within the National Security Council for the early negotiations with Cuba. Moreover, only some elements of the conflict can be undone through executive action—the embargo, in particular, runs through Congress. The domestic power structure on the Cuban side may complicate things even further—an influx of resources and goodwill could make the government more popular, but could threaten the military and other portions of government that could now lose much of their raison d’etre. Ultimately, rapprochement is often launched to strengthen embattled governments against domestic and foreign opposition. Obama’s outreach to Cuba, like his administration’s recent nuclear negotiations with Iran, follows through on his 2008 campaign pledges to engage American adversaries. However, it coincides with escalating sanctions against Venezuela. On the Cuban side, Raúl Castro declared his commitment to maintaining Cuba’s socialist, authoritarian regime—and normalizing political and potentially economic relations might help him to do just that. A win for diplomacy is not necessarily a win for democracy or for long-term cooperation, but it is a breakthrough nonetheless. Christopher Darnton is an assistant professor of politics at the Catholic University of America and the author of Rivalry and Alliance Politics in Cold War Latin America.